169 Ch 22_lecture_presentation

© 2012 Pearson Education, Inc.
PowerPoint®
Lecture Presentations prepared by
Jason LaPres
Lone Star College—North Harris
22
The Lymphatic System
and Immunity

An Introduction to the Lymphatic System and
Immunity
• Learning Outcomes
• 22-1 Distinguish between innate (nonspecific) and
adaptive (specific) defenses, and explain the
role of lymphocytes in the immune response.
• 22-2 Identify the major components of the lymphatic
system, describe the structure and functions of
each component, and discuss the importance of
lymphocytes.
• 22-3 List the body’s innate (nonspecific) defenses,
and describe the components, mechanisms,
and functions of each.

Immunity
• 22-4 Define adaptive (specific) defenses, identify the
forms and properties of immunity, and
distinguish between cell-mediated (cellular)
immunity and antibody-mediated (humoral)
immunity.
• 22-5 Discuss the types of T cells and their roles in
the immune response, and describe the
mechanisms of T cell activation and
differentiation.

Immunity
• 22-6 Discuss the mechanisms of B cell activation and
differentiation, describe the structure and
function of antibodies, and explain the primary
and secondary responses to antigen exposure.
• 22-7 Describe the development of immunological
competence, list and explain examples of
immune disorders and allergies, and discuss the
effects of stress on immune function.

Immunity
• 22-8 Describe the effects of aging on the lymphatic
system and the immune response.
• 22-9 Give examples of interactions between the
lymphatic system and other organ systems we
have studied so far and explain how the
nervous and endocrine systems influence the
immune response.

Immunity
• Pathogens
• Microscopic organisms that cause disease:
• Viruses
• Bacteria
• Fungi
• Parasites
• Each attacks in a specific way

22-1 Overview of the Lymphatic System
• The Lymphatic System
• Protects us against disease
• Lymphatic system cells respond to:
• Environmental pathogens
• Toxins
• Abnormal body cells, such as cancers

• Specific Defenses
• Lymphocytes
• Part of the immune response
• Identify, attack, and develop immunity
• To a specific pathogen

• The Immune System
• Immunity
• The ability to resist infection and disease
• All body cells and tissues involved in production of
immunity
• Not just lymphatic system

• Nonspecific Defenses
• Block or attack any potential infectious organism
• Cannot distinguish one attack from another

22-2 Structures of Body Defenses
• Organization of the Lymphatic System
1. Lymph
• A fluid similar to plasma but does not have plasma
proteins
2. Lymphatic vessels (lymphatics)
• Carry lymph from peripheral tissues to the venous
system
3. Lymphoid tissues and lymphoid organs
4. Lymphocytes, phagocytes, and other immune
system cells

Figure 22-1 An Overview of the Lymphatic System (Part 1 of 2)
Lymphatic Vessels
and Lymph Nodes
Cervical lymph nodes
Thoracic duct
Right lymphatic duct
Axillary lymph nodes
Lymphatics of
mammary gland
Cisterna chyli
Lymphatics of upper limb
Lumbar lymph nodes
Lymphoid Tissues
and Organs
Tonsil
Thymus
Spleen
Mucosa-associated
lymphoid tissue
(MALT) in digestive,
respiratory, urinary,
and reproductive
tracts
Lymph
Lymphocyte

Figure 22-1 An Overview of the Lymphatic System (Part 2 of 2)
Lymphatic Vessels
and Lymph Nodes
Inguinal lymph nodes
Lymphatics of lower limb
Lymphoid Tissues
and Organs
Appendix

• Function of the Lymphatic System
• To produce, maintain, and distribute lymphocytes
• Lymphocyte Production
• Lymphocytes are produced
• In lymphoid tissues (e.g., tonsils)
• Lymphoid organs (e.g., spleen, thymus)
• In red bone marrow
• Lymphocyte distribution
• Detects problems
• Travels into site of injury or infection

• Lymphocyte Circulation
• From blood to interstitial fluid through capillaries
• Returns to venous blood through lymphatic vessels
• The Circulation of Fluids
• From blood plasma to lymph and back to the venous
system
• Transports hormones, nutrients, and waste products

• Lymphatic Vessels
• Are vessels that carry lymph
• Lymphatic system begins with smallest vessels
• Lymphatic capillaries (terminal lymphatics)

• Lymphatic Capillaries
• Differ from blood capillaries in four ways
1. Start as pockets rather than tubes
2. Have larger diameters
3. Have thinner walls
4. Flat or irregular outline in sectional view

Figure 22-2a Lymphatic Capillaries
Smooth
muscle
Arteriole Lymphatic
capillary
Venule Interstitial
fluid
Blood capillaries Loose connective tissue
Lymph
flow
Endothelial
cells
The interwoven network formed by blood capillaries
and lymphatic capillaries.

Figure 22-2b Lymphatic Capillaries
Incomplete
basement
membrane
Lymph
flow
Lymphocyte
To larger
lymphatics
Loose
connective
tissue
Interstitial fluid
Interstitial
fluid
Blood
capillary
Lymphatic
capillary
A sectional view indicating the movement of fluid
from the plasma, through the tissues as interstitial
fluid, and into the lymphatic system as lymph.

• Lymphatic Capillaries
• Endothelial cells loosely bound together with overlap
• Overlap acts as one-way valve
• Allows fluids, solutes, viruses, and bacteria to enter
• Prevents return to intercellular space

• Lymph Flow
• From lymphatic capillaries to larger lymphatic vessels
containing one-way valves
• Lymphatic vessels travel with veins
• Lacteals
• Are special lymphatic capillaries in small intestine
• Transport lipids from digestive tract

Figure 22-3a Lymphatic Vessels and Valves
Vein
Artery
Lymphatic
vessel
Lymphatic
valve
From lymphatic
capillaries
Vein
Artery
Lymphatic
vessel
Toward
venous
system

Figure 22-3b Lymphatic Vessels and Valves
Lymphatic
vessel
Lymphatic
valve
Like valves in veins, each
lymphatic valve consists of
a pair of flaps that permit
movement of fluid in only
one direction.
Lymphatic vessel and valve LM × 63

• Lymphatic Vessels
• Superficial lymphatics
• Deep lymphatics
• Are located in:
• Skin
• Mucous membranes
• Serous membranes lining body cavities

• Superficial and Deep Lymphatics
• The deep lymphatics
• Are larger vessels that accompany deep arteries and
veins
• Superficial and deep lymphatics
• Join to form large lymphatic trunks
• Trunks empty into two major collecting vessels
1. Thoracic duct
2. Right lymphatic duct

• Major Lymph-Collecting Vessels
• The base of the thoracic duct
• Expands into cisterna chyli
• Cisterna chyli receives lymph from:
• Right and left lumbar trunks
• Intestinal trunk

• The Inferior Segment of Thoracic Duct
• Collects lymph from:
• Left bronchomediastinal trunk
• Left subclavian trunk
• Left jugular trunk
• Empties into left subclavian vein

• The Right Lymphatic Duct
• Collects lymph from:
• Right jugular trunk
• Right subclavian trunk
• Right bronchomediastinal trunk
• Empties into right subclavian vein

Figure 22-4 The Relationship between the Lymphatic Ducts and the Venous System
Right internal jugular vein
Right jugular trunk
Right subclavian trunk
Right subclavian vein
Right bronchomediastinal
trunk
Superior
vena cava (cut)
Azygos vein
Rib (cut)
Brachiocephalic veins
Drainage
of right
lymphatic
duct
Inferior vena cava (cut)
Drainage
of thoracic
duct
Right lumbar trunk
Left internal jugular vein
Left jugular trunk
Thoracic duct
Left subclavian trunk
Left bronchomediastinal
trunk
Left subclavian
vein
First rib
(cut)
Highest
intercostal
vein
Thoracic
duct
Thoracic
lymph nodes
Hemiazygos
vein
Parietal
pleura (cut)
Diaphragm
Cisterna chyli
Intestinal trunk
Left lumbar trunk

Figure 22-4a The Relationship between the Lymphatic Ducts and the Venous System
Drainage
of right
lymphatic
duct
Drainage
of thoracic
duct
The thoracic duct carries lymph
originating in tissues inferior to
the diaphragm and from the left
side of the upper body. The
smaller right lymphatic duct
delivers lymph from the rest of
the body.

Figure 22-4b The Relationship between the Lymphatic Ducts and the Venous System (Part 1 of 2)
Right internal jugular vein
Right jugular trunk
Right subclavian trunk
Right subclavian vein
Right bronchomediastinal
trunk
Superior
vena cava (cut)
Azygos vein
Rib (cut)
Brachiocephalic veins
The thoracic duct empties into the left subclavian vein. The right
lymphatic duct drains into the right subclavian vein.
Inferior vena cava (cut)
Right lumbar trunk

Figure 22-4b The Relationship between the Lymphatic Ducts and the Venous System (Part 2 of 2)
Brachiocephalic veins Left internal jugular vein
Left jugular trunk
Thoracic duct
Left subclavian trunk
Left bronchomediastinal
trunk
Left subclavian
vein
First rib
(cut)
Highest
intercostal
vein
Thoracic
duct
Thoracic
lymph nodes
Hemiazygos
vein
Parietal
pleura (cut)
Diaphragm
Cisterna chyli
Intestinal trunk
Left lumbar trunk
The thoracic duct empties into the left subclavian vein. The right
lymphatic duct drains into the right subclavian vein.

• Lymphedema
• Blockage of lymph drainage from a limb
• Causes severe swelling
• Interferes with immune system function
• Lymphocytes
• Make up 20–30% of circulating leukocytes
• Most are stored, not circulating

• Types of Lymphocytes
1. T cells
• Thymus-dependent
2. B cells
• Bone marrow–derived
3. NK cells
• Natural killer cells

• T Cells
• Make up 80% of circulating lymphocytes
• Main Types of T Cells
• Cytotoxic T (TC) cells
• Memory T cells
• Helper T (TH) cells
• Suppressor T (TS) cells

• Cytotoxic T Cells
• Attack cells infected by viruses
• Produce cell-mediated immunity
• Memory T Cells
• Formed in response to foreign substance
• Remain in body to give “immunity”
• Helper T Cells
• Stimulate function of T cells and B cells

• Suppressor T Cells
• Inhibit function of T cells and B cells
• Regulatory T Cells
• Are helper and suppressor T cells
• Control sensitivity of immune response

• Other T Cells
• Inflammatory T cells
• Suppressor/inducer T cells
• B Cells
• Make up 10–15% of circulating lymphocytes
• Differentiate (change) into plasma cells
• Plasma cells
• Produce and secrete antibodies (immunoglobulin proteins)

• Antigens
• Targets that identify any pathogen or foreign compound
• Immunoglobulins (Antibodies)
• The binding of a specific antibody to its specific target
antigen initiates antibody-mediated immunity

• Antibody-Mediated Immunity
• A chain of events that destroys the target compound or
organism
• Natural Killer (NK) Cells
• Also called large granular lymphocytes
• Make up 5–10% of circulating lymphocytes
• Responsible for immunological surveillance
• Attack foreign cells, virus-infected cells, and cancer
cells

Figure 22-5 Classes of Lymphocytes (Part 1 of 2)
Classes of Lymphocytes
subdivided into
can differentiate into
T Cells
Approximately 80% of
circulating lymphocytes are
classified as T cells.
Cytotoxic
T Cells
Helper
T Cells
Cytotoxic T cells
attack foreign cells
or body cells
infected by viruses.
Helper T cells
stimulate the
activation and
function of
both T cells
and B cells.
Suppressor T
cells inhibit
the activation
and function
of both T
cells and B
cells.
Memory T cells
are a subset of
T cells that
respond to a
previously
encountered
antigen.
Memory
T Cells
Suppressor
T Cells

Figure 22-5 Classes of Lymphocytes (Part 2 of 2)
subdivided into
B Cells
Plasma Cells
When stimulated,
B cells can
differentiate into
plasma cells, which
produce and secrete
antibodies.
B cells make up
10−15% of circulating
lymphocytes.
NK cells make
up the remaining
5−10% of
circulating
lymphocytes.
NK Cells
Classes of Lymphocytes

• Lymphocyte Distribution
• Tissues maintain different T cell and B cell populations
• Lymphocytes wander through tissues
• Enter blood vessels or lymphatics for transport
• Can survive many years

• Lymphocyte Production
• Also called lymphopoiesis, involves:
• Bone marrow
• Thymus
• Peripheral lymphoid tissues
• Hemocytoblasts
• In bone marrow, divide into two types of lymphoid stem
cells

• Lymphoid Stem Cells
• Group 1
• Remains in bone marrow and develop with help of
stromal cells
• Produces B cells and natural killer cells
• Group 2
• Migrates to thymus
• Produces T cells in environment isolated by blood–
thymus barrier

Figure 22-6a The Derivation and Distribution of Lymphocytes
Red Bone Marrow
One group of lymphoid stem
cells remains in the bone
marrow, producing daughter
cells that mature into B
cells and NK cells that
enter peripheral tissues.
Hemocytoblasts
Transported
in the
bloodstream
Mature T cell B cells
Interleukin-7
NK cells
Lymphoid stem cellsLymphoid stem cells

Figure 22-6b The Derivation and Distribution of Lymphocytes
Thymus
The second group of lymphoid
stem cells migrates to the
thymus, where subsequent
divisions produce daughter
cells that mature into T cells.
Migrate to
thymus
Mature T cell
Production and
differentiation of
T cells
Lymphoid stem cells
Thymic
hormones

• T Cells and B Cells
• Migrate throughout the body
• To defend peripheral tissues
• Retaining their ability to divide
• Is essential to immune system function

• Differentiation
• B cells differentiate
• With exposure to hormone called cytokine (interleukin-7)
• T cells differentiate
• With exposure to several thymic hormones

• Lymphoid Tissues
• Connective tissues dominated by lymphocytes
• Lymphoid Nodules
• Areolar tissue with densely packed lymphocytes
• Germinal center contains dividing lymphocytes

Figure 22-7a Lymphoid Nodules (Part 1 of 2)
Intestinal lumen
Aggregated
lymphoid nodule
Underlying
connective tissue
LM × 40Aggregated lymphoid nodules in large intestine
Aggregated lymphoid nodules in section

Figure 22-7a Lymphoid Nodules (Part 2 of 2)
Aggregated lymphoid nodules in section
Intestinal lumen
Mucous
membrane
Germinal center
Aggregated
lymphoid nodule
Underlying
connective tissue

Figure 22-7b Lymphoid Nodules
Pharyngeal
epithelium
Germinal centers
within nodules
Pharyngeal tonsil
Palate
Palatine tonsil
Lingual tonsil
positions of the tonsils and a tonsil in section. Notice the pale germinal centers, where lymphocyte cell divisions occur.
Pharyngeal tonsil LM × 20

• Distribution of Lymphoid Nodules
• Lymph nodes
• Spleen
• Respiratory tract (tonsils)
• Along digestive, urinary, and reproductive tracts

• Mucosa-Associated Lymphoid Tissue (MALT)
• Lymphoid tissues associated with the digestive
system
• Aggregated Lymphoid Nodules
• Clustered deep to intestinal epithelial lining
• Appendix (Vermiform Appendix)
• Contains a mass of fused lymphoid nodules

• The Five Tonsils
• In wall of pharynx
• Left and right palatine tonsils
• Pharyngeal tonsil (adenoid)
• Two lingual tonsils

• Lymphoid Organs
• Lymph nodes
• Thymus
• Spleen
• Are separated from surrounding tissues by a fibrous
connective tissue capsule

• Lymph Nodes
• Trabeculae
• Bundles of collagen fibers
• Extend from capsule into interior of lymph node
• Hilum
• A shallow indentation where blood vessels and nerves
reach the lymph node

• Lymph Nodes
• Afferent lymphatics
• Carry lymph
• From peripheral tissues to lymph node
• Efferent lymphatics
• Leave lymph node at hilum
• Carry lymph to venous circulation

Figure 22-8 The Structure of a Lymph Node (Part 1 of 2)
Efferent
vessel
Lymph node
artery and vein
Hilum
Lymph
vessel
Lymph
nodes
Lymph nodes
Medullary sinus
Outer cortex (B cells)
Trabeculae
Medulla
Cortex
Subcapsular
space
Deep cortex
(T cells)
Capsule Medullary cord
(B cells and
plasma cells)
Afferent
vessel

Figure 22-8 The Structure of a Lymph Node (Part 2 of 2)
Nuclei of B cells
Dendritic cells
Dividing
B cell
Capillary
Capsule
Subcapsular
space
Outer
cortex
Germinal
center

• Lymph Flow
• Flows through lymph node in a network of sinuses
• From subcapsular space
• Contains macrophages and dendritic cells
• Through outer cortex
• Contains B cells within germinal centers
• Through deep cortex
• Dominated by T cells
• Through the core (medulla)
• Contains B cells and plasma cells, organized into
medullary cords
• Finally, into hilum and efferent lymphatics

• Lymph Node Function
• A filter
• Purifies lymph before return to venous circulation
• Removes:
• Debris
• Pathogens
• 99% of antigens

• Antigen Presentation
• First step in immune response
• Extracted antigens are “presented” to lymphocytes
• Or attached to dendritic cells to stimulate lymphocytes

• Lymphatic Functions
• Lymphoid tissues and lymph nodes
• Distributed to monitor peripheral infections
• Respond before infections reach vital organs of trunk
• Lymph nodes of gut, trachea, lungs, and thoracic duct
• Protect against pathogens in digestive and respiratory
systems

• Lymph Nodes (Glands)
• Large lymph nodes at groin and base of neck
• Swell in response to inflammation
• Lymphadenopathy
• Chronic or excessive enlargement of lymph nodes
• May indicate infections, endocrine disorders, or cancer

• The Thymus
• Located in mediastinum
• Atrophies after puberty
• Diminishing effectiveness of immune system
• Divisions of the Thymus
• Thymus is divided into two thymic lobes
• Septa divide lobes into smaller lobules

• A Thymic Lobule
• Contains a dense outer cortex and a pale central
medulla
• Lymphocytes
• Divide in the cortex
• T cells migrate into medulla
• Mature T cells leave thymus by medullary blood
vessels

• Reticular Epithelial Cells in the Cortex
• Surround lymphocytes in cortex
• Maintain blood–thymus barrier
• Secrete thymic hormones that stimulate:
• Stem cell divisions
• T cell differentiation

• Reticular Epithelial Cells in the Medulla
• Form concentric layers known as thymic (Hassall’s)
corpuscles
• The medulla has no blood–thymus barrier
• T cells can enter or leave bloodstream
• Thymus Hormones
• Thymosin - an extract from the thymus that promotes
development of lymphocytes

Figure 22-9a The Thymus
Thyroid gland
Trachea
Right lobe
Diaphragm
Right
lung
THYMUS
The appearance and position of the thymus in
relation to other organs in the chest.
Left
lobe
Heart
Left
lung

Figure 22-9b The Thymus
Right
lobe
Left
lobe
Lobule
Anatomical
landmarks on
the thymus.
Septa

Figure 22-9c The Thymus
CortexSeptaMedulla
Lobule
Lobule
The thymus gland LM × 50
Fibrous septa divide the tissue of the thymus into lobules
resembling interconnected lymphoid nodules.

Figure 22-9d The Thymus
Lymphocytes
A thymic corpuscle LM × 550
Higher magnification reveals the unusual
structure of thymic corpuscles. The small
cells are lymphocytes in various stages of
development.
Thymic
corpuscle
Reticular
cells

• Three Functions of the Spleen
1. Removal of abnormal blood cells and other blood
components by phagocytosis
2. Storage of iron recycled from red blood cells
3. Initiation of immune responses by B cells and T cells
• In response to antigens in circulating blood

• Anatomy of the Spleen
• Attached to stomach by gastrosplenic ligament
• Contacts diaphragm and left kidney
• Splenic veins, arteries, and lymphatic vessels
• Communicate with spleen at hilum

• Histology of the Spleen
• Inside fibrous capsule
• Red pulp contains many red blood cells
• White pulp resembles lymphoid nodules

• Trabecular Arteries
• Branch and radiate toward capsule
• Finer branches surrounded by white pulp
• Capillaries discharge red blood cells into red pulp
• Red Pulp
• Contains elements of circulating blood
• Plus fixed and free macrophages

• Splenic Circulation
• Blood passes through:
• Network of reticular fibers
• Then enters large sinusoids (lined by macrophages)
• Which empty into trabecular veins

Figure 22-10a The Spleen
Spleen
Rib
Pancreas
Aorta
Parietal peritoneum
Visceral peritoneum
Stomach
Diaphragm
Gastrosplenic
ligament
Gastric area
Diaphragmatic surface
SPLEEN
Hilum
Renal area
Kidneys
Liver

Figure 22-10b The Spleen
SUPERIOR
Gastric
area
Hilum
Splenic vein
Splenic artery
Splenic
lymphatic
vessel
Renal
area
INFERIOR
A posterior view of the surface of an intact
spleen, showing major anatomical landmarks.

Figure 22-10c The Spleen
The histological appearance of the spleen. White pulp is
dominated by lymphocytes; it appears purple because
the nuclei of lymphocytes stain very darkly. Red pulp
contains a large number of red blood cells.
The spleen LM × 50
White pulp of
splenic nodule
Capsule
Red pulp
Trabecular
artery
Central artery in
splenic nodule

• Spleen Function
• Phagocytes and other lymphocytes in spleen
• Identify and attack damaged and infected cells
• In circulating blood

• The Lymphatic System and Body Defenses
• Body defenses provide resistance to fight infection,
illness, and disease
• Two categories of defenses
1. Innate (nonspecific) defenses
2. Adaptive (specific) defenses

• Innate (Nonspecific) Defenses
• Always work the same way
• Against any type of invading agent
• Nonspecific resistance
• Adaptive (Specific) Defenses
• Protect against specific pathogens
• Depend on activities of lymphocytes
• Specific resistance (immunity)
• Develops after exposure to environmental hazards

22-3 Nonspecific Defenses
• Seven Major Categories of Innate (Nonspecific)
Defenses
1. Physical barriers
2. Phagocytes
3. Immunological surveillance
4. Interferons
5. Complement
6. Inflammatory response
7. Fever

• Physical Barriers
• Keep hazardous materials outside the body
• Phagocytes
• Attack and remove dangerous microorganisms
• Immunological Surveillance
• Constantly monitors normal tissues
• With natural killer cells (NK cells)

• Interferons
• Chemical messengers that trigger production of
antiviral proteins in normal cells
• Antiviral proteins
• Do not kill viruses
• Block replication in cell
• Complement
• System of circulating proteins
• Assists antibodies in destruction of pathogens

• Inflammatory Response
• Localized, tissue-level response that tends to limit
spread of injury or infection
• Fever
• A high body temperature
• Increases body metabolism
• Accelerates defenses
• Inhibits some viruses and bacteria

Figure 22-11 Innate Defenses (Part 1 of 2)
Innate Defenses
Physical barriers
keep hazardous
organisms and
materials outside
the body.
Phagocytes
engulf pathogens
and cell debris.
Immunological
surveillance
is the destruction of
abnormal cells by NK
cells in peripheral tissues.
Interferons
are chemical messengers
that coordinate the
defenses against viral
infections.
Duct of eccrine
sweat gland Hair
Fixed
macrophage Neutrophil
Free
macrophage
Natural
killer cell
Lysed
abnormal
cell
Eosinophil Monocyte
Secretions
Epithelium
Interferons released by activated
lymphocytes, macrophages, or
virus-infected cells

Figure 22-11 Innate Defenses (Part 2 of 2)
Complement
system
consists of circulating
proteins that assist
antibodies in the
destruction of pathogens.
is a localized, tissue-level
response that tends to
limit the spread of an
injury or infection.
Inflammatory
response
is an elevation of body
temperature that accelerates
tissue metabolism and the
activity of defenses.
Fever
Mast cell
Complement
Lysed
pathogen
Body temperature rises above 37.2ºC in
response to pyrogens
1. Blood flow increased
2. Phagocytes activated
3. Capillary permeability increased
7. Adaptive defenses activated
4. Complement activated
5. Clotting reaction walls off region
6. Regional temperature increased
Innate Defenses

• Physical Barriers
• Outer layer of skin
• Hair
• Epithelial layers of internal passageways
• Secretions that flush away materials
• Sweat glands, mucus, and urine
• Secretions that kill or inhibit microorganisms
• Enzymes, antibodies, and stomach acid

• Two Classes of Phagocytes
1. Microphages
• Neutrophils and eosinophils
• Leave the bloodstream
• Enter peripheral tissues to fight infections

• Two Classes of Phagocytes
2. Macrophages
• Large phagocytic cells derived from monocytes
• Distributed throughout body
• Make up monocyte–macrophage system
(reticuloendothelial system)

• Activated Macrophages
• Respond to pathogens in several ways
• Engulf pathogen and destroy it with lysosomal
enzymes
• Bind to pathogen so other cells can destroy it
• Destroy pathogen by releasing toxic chemicals into
interstitial fluid

• Two Types of Macrophages
1. Fixed macrophages
• Also called histiocytes
• Stay in specific tissues or organs
• For example, dermis and bone marrow
2. Free macrophages
• Also called wandering macrophages
• Travel throughout body

• Special Histiocytes
• Microglia found in central nervous system
• Kupffer cells found in liver sinusoids
• Free Macrophages
• Special free macrophages
• Alveolar macrophages (phagocytic dust cells)

• Movement and Phagocytosis
• All macrophages:
• Move through capillary walls (emigration)
• Are attracted or repelled by chemicals in surrounding
fluids (chemotaxis)
• Phagocytosis begins:
• When phagocyte attaches to target (adhesion)
• And surrounds it with a vesicle

• Is carried out by natural killer (NK) cells
• Activated NK Cells
1. Identify and attach to abnormal cell (nonselective)
2. Golgi apparatus in NK cell forms perforin vesicles
3. Vesicles release proteins called perforins (exocytosis)
4. Perforins lyse abnormal plasma membrane
• Also attack cancer cells and cells infected with
viruses

Figure 22-12 How Natural Killer Cells Kill Cellular Targets (Step 1)
Recognition and
Adhesion
NK cellGolgi apparatus
Abnormal
cell

Realignment of
Golgi apparatus

Secretion of Perforin
Perforin
molecules
NK
cell
Abnormal
cell
Pores formed
by perforin
complex

Lysis of Abnormal Cell

• Cancer cells
• With tumor-specific antigens
• Are identified as abnormal by NK cells
• Some cancer cells avoid NK cells
(immunological escape)

• Viral infections
• Cells infected with viruses
• Present abnormal proteins on plasma
membranes
• Allow NK cells to identify and destroy them

• Interferons
• Proteins (cytokines) released by activated lymphocytes
and macrophages
• Cytokines
• Chemical messengers released by tissue cells
• To coordinate local activities
• To act as hormones to affect whole body

• Three Types of Interferons
1. Alpha-interferons
• Produced by leukocytes
• Stimulate NK cells
2. Beta-interferons
• Secreted by fibrocytes
• Slow inflammation
3. Gamma-interferons
• Secreted by T cells and NK cells
• Stimulate macrophage activity

Figure 22-13 Interferons
Alpha (α)-interferons are
produced by cells infected
with viruses. They attract
and stimulate NK cells and
enhance resistance to viral
infection.
Beta (β)-interferons,
secreted by fibroblasts,
slow inflammation in a
damaged area.
Gamma (γ)-interferons,
secreted by T cells and NK
cells, stimulate
macrophage activity.

• Complement
• Plasma contains 11 special complement (C) proteins
• That form complement system and complement
antibody action
• Complement activation
• Complements work together in cascades
• Two pathways activate the complement system
1. Classical pathway
2. Alternative pathway

• Complement Activation: The Classical Pathway
• Fast method C1 binds to:
• Antibody molecule attached to antigen (bacterium)
• Bound protein acts as enzyme
• Catalyzes chain reaction

Figure 22-14 Pathways of Complement Activation (Part 2 of 3)
The most rapid and effective activation
of the complement system occurs
through the classical pathway.
Activation and Cascade
C3b Attachment
(classical pathway)
C3b Attachment
(alternate pathway)
The classical pathway
ends with the conversion
of an inactive C3 to an
activated C3b that
attaches to the cell wall.
The attached C1 protein
then acts as an enzyme,
catalyzing a series of
reactions involving other
complement proteins.
C3b
C3bC3b
C3C2
C1
C1 attachment
Classical Pathway
Antibody Binding and
C1 Attachment
Antibody binding
Antibodies
Bacterial
cell wall
C4

• Complement Activation: The Alternative Pathway
• Slow method exposed to antigen
• Factor P (properdin)
• Factor B
• Factor D
• Interact in plasma

Figure 22-14 Pathways of Complement Activation (Part 1 of 3)
The alternative
pathway is important
in the defense
against bacteria,
some parasites, and
virus-infected cells.
Alternative Pathway
C3
C3b
The alternative pathway begins
when several complement
proteins, notably properdin,
interact in the plasma. This
interaction can be triggered by
exposure to foreign materials,
such as the capsule of a
bacterium. The end result is the
attachment of an activated C3b
protein to the bacterial cell wall.
Properdin
Factor B
Factor D
Bacterial
cell wall

• Complement Activation
• Both pathways end with:
• Conversion of inactive complement protein C3
• To active form C3b
ANIMATION Immunity: Complement

• Effects of Complement Activation
• Pore formation
• Destruction of target plasma membranes
• Five complement proteins join to form membrane
attack complex (MAC)
• Enhancement of phagocytosis by opsonization
• Complements working with antibodies (opsonins)
• Histamine release
• Increases the degree of local inflammation and blood flow

• Inflammation
• Also called inflammatory response
• A localized response
• Triggered by any stimulus that kills cells or injures
tissue

• Cardinal Signs and Symptoms
• Swelling (tumor)
• Redness (rubor)
• Heat (calor)
• Pain (dolor)

• Three Effects of Inflammation
1. Temporary repair and barrier against pathogens
2. Retards spread of pathogens into surrounding areas
3. Mobilization of local and systemic defenses
• And facilitation of repairs (regeneration)

Figure 22-15 Inflammation and the Steps in Tissue Repair (Part 1 of 2)
Tissue Damage
Mast Cell Activation
Chemical change
in interstitial fluid
Release of
histamine and
heparin from
mast cells

Figure 22-15 Inflammation and the Steps in Tissue Repair (Part 2 of 2)
Redness, Swelling, Warmth, and Pain Phagocyte Attraction
Attraction of
phagocytes,
especially
neutrophils
Release of
cytokines
Dilation of
blood vessels,
increased blood
flow, increased
vessel
permeability
Clot
formation
(temporary
repair)
Removal of
debris by
neutrophils
and macro-
phages;
stimulation of
fibroblasts
Activation
of specific
defenses
Pathogen
removal, clot
erosion, scar
tissue formation
Tissue Repair

• Products of Inflammation
• Necrosis
• Local tissue destruction in area of injury
• Pus
• Mixture of debris and necrotic tissue
• Abscess
• Pus accumulated in an enclosed space

• Fever
• A maintained body temperature above 37°C (99°F)
• Pyrogens
• Any material that causes the hypothalamus to raise
body temperature
• Circulating pathogens, toxins, or antibody complexes
• Endogenous pyrogens or interleukin-1 (IL-1)
• Pyrogen released by active macrophages
• A cytokine
ANIMATION Immunity: Nonspecific Defenses

22-4 Specific Defenses
• Adaptive (Specific) Defenses
• Specific resistance (immunity)
• Responds to specific antigens
• With coordinated action of T cells and B cells

• Specific Defenses
• T Cells
• Provide cell-mediated immunity
• Defend against abnormal cells and pathogens
inside cells
• B Cells
• Provide antibody-mediated immunity
• Defend against antigens and pathogens in body
fluids

• Forms of Immunity
1. Innate
• Present at birth
2. Adaptive
• After birth
3. Active
• Antibodies develop after exposure to antigen
4. Passive
• Antibodies are transferred from another source

• Active Immunity
• Naturally acquired
• Through environmental exposure to pathogens
• Artificially induced
• Through vaccines containing pathogens

• Passive Immunity
• Naturally acquired
• Antibodies acquired from the mother
• Artificially induced
• By an injection of antibodies

Figure 22-16 Forms of Immunity
Immunity
Response to threats on an
individualized basis
Adaptive Immunity
Active Immunity Passive Immunity
Adaptive immunity is not present at birth; you
acquire immunity to a specific antigen only when
you have been exposed to that antigen or receive
antibodies from
another source.
Develops in response
to antigen exposure
Develops after
exposure to
antigens in
environment
Develops after
administration of
an antigen to
prevent disease
Conferred by
transfer of maternal
antibodies across
placenta or in
breast milk
Conferred by
administration of
antibodies to
combat infection
Naturally acquired
active immunity
Artificially induced
active immunity
Naturally acquired
passive immunity
Artificially induced
passive immunity
Genetically
determined−no
prior exposure or
antibody
production
involved
Innate Immunity
Produced by transfer
of antibodies from
another source

• Four Properties of Immunity
1. Specificity
• Each T or B cell responds only to a specific antigen and
ignores all others
2. Versatility
• The body produces many types of lymphocytes
• Each fights a different type of antigen
• Active lymphocyte clones itself to fight specific
antigen

• Four Properties of Immunity
3. Memory
• Some active lymphocytes (memory cells):
• Stay in circulation
• Provide immunity against new exposure
3. Tolerance
• Immune system ignores “normal” antigens (self-
antigens)

• An Introduction to the Immune Response
• Two main divisions
1. Cell-mediated immunity (T cells)
2. Antibody-mediated immunity (B cells)

Figure 22-17 An Overview of the Immune Response
Adaptive Defenses
Cell-Mediated
Immunity
Direct Physical and
Chemical Attack
Antibody-Mediated
Immunity
Attack by Circulating
Antibodies
Destruction
of antigens
Phagocytes
activated
T cells
activated
Communication
and feedback
Antigen presentation
triggers specific
defenses, or an
immune response.
Activated B
cells give rise
to cells that
produce
antibodies.
Activated T cells find
the pathogens and
attack them through
phagocytosis or the
release of chemical
toxins.

22-5 T Cells and Immunity
• Four Major Types of T Cells
1. Cytotoxic T cells (also called TC cells)
• Attack cells infected by viruses
• Responsible for cell-mediated immunity
2. Memory T cells
• Clone more of themselves in response to “remembered”
antigen
3. Helper T cells (also called TH cells)
• Stimulate function of T cells and B cells
• Suppressor T cells (also called TS cells)
1.Inhibit function of T cells and B cells

• Antigen Presentation
• T cells only recognize antigens that are bound to
glycoproteins in plasma membranes
• MHC Proteins
• The membrane glycoproteins that bind to antigens
• Genetically coded in chromosome 6
• The major histocompatibility complex (MHC)
• Differs among individuals

• Two Classes of MHC Proteins
• Class I
• Found in membranes of all nucleated cells
• Class II
• Found in membranes of antigen-presenting cells
(APCs)
• Found in lymphocytes

• Class I MHC Proteins
• Pick up small peptides in cell and carry them to the
surface
• T cells ignore normal peptides
• Abnormal peptides or viral proteins activate T cells to
destroy cell

Figure 22-18a Antigens and MHC Proteins
Antigen presentation
by Class I MHC
proteins is triggered by
viral or bacterial
infection of a body cell.
The infection results
in the appearance of
abnormal peptides in
the cytoplasm.
The abnormal peptides
are incorporated into
Class I MHC proteins
as they are synthesized
at the endoplasmic
reticulum.
Plasma membrane
Viral or bacterial
pathogen
Transport
vesicle
Endoplasmic
reticulum
Nucleus
The abnormal
peptides are
displayed by Class I
MHC proteins on the
plasma membrane.
After export to the
Golgi apparatus, the
MHC proteins reach
the plasma
membrane within
transport vesicles.
Infected cell

• Class II MHC Proteins
• Antigenic Fragments
• From antigenic processing of pathogens
• Bind to Class II proteins
• Inserted in plasma membrane to stimulate T cells
• Antigen-Presenting Cells (APCs)
• Responsible for activating T cells against foreign cells
and proteins

Figure 22-18b Antigens and MHC Proteins
Antigenic fragments are
displayed by Class II
MHC proteins on the
plasma membrane.
Antigenic fragments
are bound to Class II
MHC proteins.
The endoplasmic
reticulum produces
Class II MHC proteins.
Plasma
membrane
Endoplasmic
reticulum
Nucleus
Lysosome
Phagocytic antigen-presenting cell
Lysosomal action
produces antigenic
fragments.
Phagocytic APCs
engulf the extracellular
pathogens.

• Phagocytic APCs
1. Free and fixed macrophages
• In connective tissues
2. Kupffer cells
• Of the liver
3. Microglia
• In the CNS

• Non-phagocytic APCs
• Langerhans cells
• In the skin
• Dendritic cells
• In lymph nodes and spleen

• Antigen Recognition
• Inactive T cell receptors
• Recognize Class I or Class II MHC proteins
• Recognize a specific antigen
• Binding occurs when MHC protein matches antigen

• CD Markers
• Also called cluster of differentiation markers
• In T cell membranes
• Molecular mechanism of antigen recognition
• More than 70 types
• Designated by an identifying number
• CD3 Receptor Complex
• Found in all T cells

• Two Important CD Markers
1. CD8 Markers
• Found on cytotoxic T cells and suppressor T cells
• Respond to antigens on Class I MHC proteins
2. CD4 Markers
• Found on helper T cells
• Respond to antigens on Class II MHC proteins
• CD8 or CD4 Markers
• Bind to CD3 receptor complex
• Prepare cell for activation

• Costimulation
• For T cell to be activated, it must be costimulated
• By binding to stimulating cell at second site
• Which confirms the first signal

• Activation of CD8 T Cells
• Activated by exposure to antigens on MHC proteins
• One responds quickly
• Producing cytotoxic T cells and memory T cells
• The other responds slowly
• Producing suppressor T cells

• Cytotoxic T Cells
• Seek out and immediately destroy target cells
1. Release perforin
• To destroy antigenic plasma membrane
2. Secrete poisonous lymphotoxin
• To destroy target cell
3. Activate genes in target cell
• That cause cell to die

Figure 22-19 Antigen Recognition by and Activation of Cytotoxic T Cells (Steps 1-3)
Antigen Recognition Activation and
Cell Division
Infected cell
Inactive
CD8
T cell
Viral or
bacterial antigen
Antigen recognition occurs
when a CD8 T cell encounters
an appropriate antigen on the
surface of another cell, bound
to a Class I MHC protein.
Antigen recognition results
in T cell activation and cell
division, producing active TC
cells and memory TC cells.
Active
TC cell
Memory
TC cells
(inactive)
Infected
cell
CD8
protein
Class I
MHC
T cell
receptor
CD8
T cell
Antigen
Costimulation
activates
CD8 T cell
Before activation
can occur, a
T cell must be
chemically or
physically
stimulated by
the abnormal
target cell.
Costimulation

Figure 22-19 Antigen Recognition by and Activation of Cytotoxic T Cells (Steps 4)
Destruction of Target Cells
The active TC cell destroys the
antigen-bearing cell. It may use
several different mechanisms to
kill the target cell.
Lysed
cell
Perforin release
Destruction of
plasma membrane
Stimulation of
apoptosis
Disruption of cell
metabolism
Cytokine
release
Lymphotoxin
release

• Memory TC Cells
• Produced with cytotoxic T cells
• Stay in circulation
• Immediately form cytotoxic T cells if same antigen
appears again

• Suppressor T Cells
• Secrete suppression factors
• Inhibit responses of T and B cells
• Act after initial immune response
• Limit immune reaction to single stimulus

• Activation of CD4 T cells
• Active helper T cells (TH cells)
• Secrete cytokines
• Memory helper (TH) cells
• Remain in reserve

Figure 22-20 Antigen Recognition and Activation of Helper T Cells (Part 1 of 2)
Antigen Recognition by CD4 T Cell
Foreign antigen
Antigen-presenting
cell (APC)
Class II MHC
APC
Antigen
T cell receptor
Costimulation
CD4 protein
TH cell
Inactive
CD4 (TH)
cell

Figure 22-20 Antigen Recognition and Activation of Helper T Cells (Part 2 of 2)
CD4 T Cell Activation and Cell Division
Memory TH cells
(inactive)
Active
TH cells
Cytokines
Active helper T cells secrete
cytokines that stimulate both
cell-mediated and
antibody-mediated immunity.
Cytokines
Cytokines

• Four Functions of Cytokines
1. Stimulate T cell divisions
• Produce memory TH cells
• Accelerate cytotoxic T cell maturation
2. Attract and stimulate macrophages
3. Attract and stimulate activity of cytotoxic T cells
4. Promote activation of B cells

Figure 22-21a A Summary of the Pathways of T Cell Activation
Activation by Class I MHC proteins
Antigen bound to
Class I MHC protein
Indicates that the cell is infected
or otherwise abnormal
CD8 T Cells
Cytotoxic T Cells Memory TC Cells
Attack and destroy
infected and
abnormal cells
displaying antigen
Await
reappearance
of the antigen
Control or moderate
immune response by
T cells and B cells
Suppressor T Cells

Figure 22-21b A Summary of the Pathways of T Cell Activation
Activation by Class II MHC proteins
Helper T Cells
Stimulate immune
response by
T cells and B cells
Await
reappearance
of the antigen
Memory TH Cells
CD4 T Cells
Indicates presence of pathogens,
toxins, or foreign proteins
Antigen bound to
Class II MHC protein

22-6 B Cells and Immunity
• B Cells
• Responsible for antibody-mediated immunity
• Attack antigens by producing specific antibodies
• Millions of populations, each with different antibody
molecules

• B Cell Sensitization
• Corresponding antigens in interstitial fluids bind to
B cell receptors
• B cell prepares for activation
• Preparation process is sensitization
• During sensitization, antigens are:
• Taken into the B cell
• Processed
• Reappear on surface, bound to Class II MHC
protein

Figure 22-22 The Sensitization and Activation of B Cells (Step 1)
Sensitization
Sensitized
B cell
Antigen
binding
Antigens bound to
antibody molecules
Antigens
Class II MHC
Antibodies
Inactive B cell

• Helper T Cells
• Sensitized B cell is prepared for activation but needs
helper T cell activated by same antigen
• B Cell Activation
• Helper T cell binds to MHC complex
• Secretes cytokines that promote B cell activation and
division

Activation
Cytokine
costimulation
Helper T cell
T cell
Sensitized
B cell
B cell
Class II MHC T cell receptor
Antigen

• B Cell Division
• Activated B cell divides into:
• Plasma cells
• Memory B cells

Division and Differentiation
Plasma cells
ANTIBODY
PRODUCTION
Activated B cells
Memory B cells
(inactive)

• Plasma Cells
• Synthesize and secrete antibodies into interstitial fluid
• Memory B Cells
• Like memory T cells, remain in reserve to respond to
next infection

• Antibody Structure
• Two parallel pairs of polypeptide chains
• One pair of heavy chains
• One pair of light chains
• Each chain contains:
• Constant segments
• Variable segments

• Five Heavy-Chain Constant Segments
• Determine five types of antibodies
1. IgG
2. IgE
3. IgD
4. IgM
5. IgA

• Variable Segments of Light and Heavy Chains
• Determine specificity of antibody molecule
• Binding Sites
• Free tips of two variable segments
• Form antigen binding sites of antibody molecule
• Which bind to antigenic determinant sites of antigen
molecule
• Antigen–Antibody Complex
• An antibody bound to an antigen

• The Antigen–Antibody Complex
• A Complete Antigen
• Has two antigenic determinant sites
• Binds to both antigen-binding sites of variable segments
of antibody
• B Cell Sensitization
• Exposure to a complete antigen leads to:
• B cell sensitization
• Immune response

• Hapten (Partial Antigens)
• Must attach to a carrier molecule to act as a complete
antigen
• Dangers of Haptens
• Antibodies produced will attack both hapten and carrier
molecule
• If carrier is “normal”:
• Antibody attacks normal cells
• For example, penicillin allergy

Figure 22-23a Antibody Structure and Function
Antigen
binding
site
Variable
segment
Constant
segments
of light
and heavy
chains
Heavy chain
Disulfide
bond
Antigen
binding site
Light
chain
Complement
binding site
Site of binding
to macrophages
A diagrammatic view of the structure of an antibody.

Figure 22-23b Antibody Structure and Function
A computer-generated image of a
typical antibody.
Light
chain
Heavy
chain
Antigen
binding site

Figure 22-23c Antibody Structure and Function
Antigen
Antigenic
determinant
sites
Antibodies
Antibodies bind to portions of
an antigen called antigenic
determinant sites, or epitopes.

Figure 22-23d Antibody Structure and Function
Antibody molecules can bind a
hapten (partial antigen) once it has
become a complete antigen by
combining with a carrier molecule.
Complete
antigen
Hapten
Carrier
molecule

• Five Classes of Antibodies
• Also called immunoglobulins (Igs)
• IgG, IgD, IgE, IgM, IgA
• Are found in body fluids
• Are determined by constant segments
• Have no effect on antibody specificity

• IgG is the largest and most diverse class of antibodies
• 80 percent of all antibodies
• IgG antibodies are responsible for resistance against
many viruses, bacteria, and bacterial toxins
• Can cross the placenta, and maternal IgG provides
passive immunity to fetus during embryological
development
• Anti-Rh antibodies produced by Rh-negative mothers
are also IgG antibodies and produce hemolytic disease
of the newborn

• IgE attaches as an individual molecule to the exposed
surfaces of basophils and mast cells
• When an antigen is bound by IgE molecules:
• The cell is stimulated to release histamine and other
chemicals that accelerate inflammation in the
immediate area
• IgE is also important in the allergic response

• IgD is an individual molecule on the surfaces of B
cells, where it can bind antigens in the extracellular
fluid
• Binding can play a role in the sensitization of the B
cell involved

• IgM is the first class of antibody secreted after an
antigen is encountered
• IgM concentration declines as IgG production
accelerates
• Plasma cells secrete individual IgM molecules, but it
polymerizes and circulates as a five-antibody starburst
• The anti-A and anti-B antibodies responsible for the
agglutination of incompatible blood types are IgM
antibodies
• IgM antibodies may also attack bacteria that are
insensitive to IgG

• IgA is found primarily in glandular secretions such as
mucus, tears, saliva, and semen
• Attack pathogens before they gain access to internal
tissues
• IgA antibodies circulate in blood as individual
molecules or in pairs
• Epithelial cells absorb them from blood and attach a
secretory piece, which confers solubility, before
secreting IgA molecules onto the epithelial surface

Table 22-1 Classes of Antibodies (Part 1 of 2)

Table 22-1 Classes of Antibodies (Part 2 of 2)
Secretory
piece

• Seven Functions of Antigen–Antibody Complexes
1. Neutralization of antigen binding sites
2. Precipitation and agglutination - formation of
immune complex
3. Activation of complement
4. Attraction of phagocytes
5. Opsonization increasing phagocyte efficiency
6. Stimulation of inflammation
7. Prevention of bacterial and viral adhesion

• Primary and Secondary Responses to Antigen
Exposure
• Occur in both cell-mediated and antibody-mediated
immunity
• First exposure
• Produces initial primary response
• Next exposure
• Triggers secondary response
• More extensive and prolonged
• Memory cells already primed

• The Primary Response
• Takes time to develop
• Antigens activate B cells
• Plasma cells differentiate
• Antibody titer (level) slowly rises

• The Primary Response
• Peak response
• Can take two weeks to develop
• Declines rapidly
• IgM
• Is produced faster than IgG
• Is less effective

Figure 22-24a The Primary and Secondary Responses in Antibody-Mediated Immunity
Time (weeks)
IgG
IgM
Antibody
concentrationinserum
PRIMARY
RESPONSE

• The Secondary Response
• Activates memory B cells
• At lower antigen concentrations than original B cells
• Secrete antibodies in massive quantities

Figure 22-24b The Primary and Secondary Responses in Antibody-Mediated Immunity
Time (weeks)
IgM
SECONDARY
RESPONSE
IgG

• Effects of Memory B Cell Activation
• IgG
• Rises very high and very quickly
• Can remain elevated for extended time
• IgM
• Production is also quicker
• Slightly extended

• Combined Responses to Bacterial Infection
• Neutrophils and NK cells begin killing bacteria
• Cytokines draw phagocytes to area
• Antigen presentation activates:
• Helper T cells
• Cytotoxic T cells
• B cells activate and differentiate
• Plasma cells increase antibody levels

Figure 22-25 The Course of the Body’s Response to a Bacterial Infection
Neutrophils Macrophages Plasma cells
Antibody
titer
Cytotoxic
T cells
Natural
killer cells
Time (weeks)
Numberofactiveimmunecells

• Combined Responses to Viral Infection
• Similar to bacterial infection
• But cytotoxic T cells and NK cells are activated by
contact with virus-infected cells

Figure 22-27a Defenses against Bacterial and Viral Pathogens
BACTERIA
Phagocytosis by
macrophages and APCs
Antigen
presentation
Activation of
cytotoxic T cells
Activation of
helper T cells
Activation
of B cells
Antibody
production by
plasma cells
Destruction of
bacteria by
cell lysis or
phagocytosis
Opsonization
and phagocyte
attraction
Formation of
antigen−antibody
complexes
Defenses against bacteria involve phagocy-
tosis and antigen presentation by APCs.

Figure 22-27b Defenses against Bacterial and Viral Pathogens
Release of
interferons
Infection of
tissue cells
Appearance of antigen
in plasma membrane
Infection of or uptake
by APCs
VIRUSES
Antigen
presentation
Activation of
helper T cells
Activation
of B cells
Antibody
production by
plasma cells
Destruction of
viruses or
prevention of
virus entry into cells
Increased
resistance to
viral infection
and spread
Stimulation
of NK cells
Activation of
cytotoxic T cells
Destruction of
virus-infected cells
Defenses against viruses involves direct contact with virus-infected cells
and antigen presentation by APCs.

Table 22-2 Cells That Participate in Tissue Defenses (Part 1 of 2)

Table 22-2 Cells That Participate in Tissue Defenses (Part 2 of 2)

22-7 Immune System Development
• Immune System Development
• Fetus can produce immune response (has
immunological competence)
• After exposure to antigen
• At about three to four months

• Development of Immunological Competence
• Fetal thymus cells migrate to tissues that form T cells
• Liver and bone marrow produce B cells
• Four month fetus produces IgM antibodies

• Before Birth
• Maternal IgG antibodies
• Pass through placenta
• Provide passive immunity to fetus
• After Birth
• Mother’s milk provides IgA antibodies
• While passive immunity is lost

• Normal Resistance
• Infant produces IgG antibodies through exposure to
antigens
• Antibody, B cell, and T cell levels slowly rise to adult
levels
• About age 12

• Cytokines of the Immune System
• Chemical messengers involved in cellular immunity
• Hormones and paracrine-like glycoproteins
• Examples of cytokines:
• Interferons
• Interleukins
• Tumor necrosis factors (TNFs)

• Interleukins
• Functions include:
1. Increasing T cell sensitivity to antigens exposed on
macrophage membranes
2. Stimulating B cell activity, plasma cell formation and
antibody production

• Interleukins
• Functions include:
3. Enhancing nonspecific defenses
• Stimulation of inflammation
• Formation of scar tissue by fibroblasts
• Elevation of body temperature via the preoptic nucleus
of the hypothalamus
• Stimulation of mast cell formation
• Promotion of adrenocorticotroic hormone (ACTH)
secretion by the anterior lobe of the pituitary gland
3. Moderating the immune response
• Some interleukins help suppress immune function and
shorten the immune response

• Interleukins
• IL-1 and IL2, are important in stimulating and
maintaining the immune response
• When released by activated macrophages and
lymphocytes, these cytokines stimulate the activities
of other immune cells and of the secreting cell
• Result is a positive feedback loop that helps to recruit
additional immune cells

• Three Types of Interferons
1. Alpha-interferons
• Produced by leukocytes
• Stimulate NK cells
2. Beta-interferons
• Secreted by fibrocytes
• Slow inflammation
3. Gamma-interferons
• Secreted by T cells and NK cells
• Stimulate macrophage activity

• Tumor Necrosis Factors (TNFs)
• TNFs slow the growth of a tumor and kill sensitive tumor
cells
• Activated macrophages secrete one type of TNF and
carry the molecules in their plasma membranes
• Cytotoxic T cells produce a different type of TNF
• In addition to their effects on tumor cells:
• TNFs stimulate granular leukocyte production, promote
eosinophil activity, cause fever, and increase T cell
sensitivity to interleukins

• Phagocyte-Activating Chemicals
• Several cytokines coordinate immune defenses by
adjusting the activities of phagocytic cells
• Include factors that attract free macrophages and
microphages and prevent their premature departure from
the site of an injury
• Colony-Stimulating Factors
• Factors are produced by active T cells, cells of the
monocyte-macrophage group, endothelial cells, and
fibrocytes
• CSFs stimulate the production of blood cells in red bone
marrow and lymphocytes in lymphoid tissues and organs

• Cytokines are Often Classified According to their
Origins
• Lymphokines are produced by lymphocytes
• Monokines are secreted by active macrophages and
other antigen-presenting cells
• These terms are misleading, because lymphocytes and
macrophages may secrete the same cytokines
• Cells involved in adaptive defenses and tissue repair
can also secrete cytokines

• Immune Disorders
• Autoimmune disorders
• Immunodeficiency disease
• Allergies

• Autoimmune Disorders
• A malfunction of system that recognizes and ignores
“normal” antigens
• Activated B cells make autoantibodies against body
cells
• Examples:
• Thyroiditis
• Rheumatoid arthritis
• Insulin-dependent diabetes mellitus (IDDM)

• Immunodeficiency Diseases
• Result from:
• Problems with embryological development of lymphoid
tissues
• Can result in severe combined
immunodeficiency disease (SCID)
• Viral infections such as HIV
• Can result in AIDS
• Immunosuppressive drugs or radiation treatments
• Can lead to complete immunological failure

• Allergies
• Inappropriate or excessive immune responses to
antigens
• Allergens
• Antigens that trigger allergic reactions

• Four Categories of Allergic Reactions
1. Immediate hypersensitivity Type I
2. Cytotoxic reactions Type II
3. Immune complex disorders Type III
4. Delayed hypersensitivity Type IV

• Type I Allergy
• Also called immediate hypersensitivity
• A rapid and severe response to the presence of an
antigen
• Most commonly recognized type of allergy
• Includes allergic rhinitis (environmental allergies)

• Type I Allergy
• Sensitization leads to:
• Production of large quantities of IgE antibodies
distributed throughout the body
• Second exposure leads to:
• Massive inflammation of affected tissues

• Type I Allergy
• Severity of reaction depends on:
• Individual sensitivity
• Locations involved
• Allergens (antigens that trigger reaction) in
bloodstream may cause anaphylaxis

• Anaphylaxis
• Can be fatal
• Affects cells throughout body
• Changes capillary permeability
• Produces swelling (hives) on skin
• Smooth muscles of respiratory system contract
• Make breathing difficult
• Peripheral vasodilatation
• Can cause circulatory collapse (anaphylactic shock)

Figure 22-29 The Mechanism of Anaphylaxis (Part 1 of 2)
First
Exposure Allergen fragment
Allergens
Macrophage
B cell sensitization
and activation
TH cell activation
Plasma cell
IgE antibodies

Figure 22-29 The Mechanism of Anaphylaxis (Part 2 of 2)
IgE
Granules
Massive
stimulation of
mast cells
and basophils
Sensitization of
mast cells and
basophils
Subsequent
Exposure
Release of histamines, leukotrienes,
and other chemicals that
cause pain and inflammation
Capillary dilation, increased capillary
permeability, airway constriction,
mucus secretion, pain and itching
Allergen

• Antihistamines
• Drugs that block histamine released by mast cells
• Can relieve mild symptoms of immediate
hypersensitivity
• Benadryl

• Stress and the Immune Response
• Glucocorticoids
• Secreted to limit immune response
• Long-term secretion (chronic stress)
• Inhibits immune response
• Lowers resistance to disease

• Functions of Glucocorticoids
• Depression of the inflammatory response
• Reduction in abundance and activity of
phagocytes
• Inhibition of interleukin secretion

22-8 Effects of Aging on the Immune System
• Immune System Diminishes with Age
• Increasing vulnerability to infections and cancer
• Four Effects of Aging
1. Thymic hormone production is greatly reduced
2. T cells become less responsive to antigens
3. Fewer T cells reduces responsiveness of B cells
4. Immune surveillance against tumor cells declines

22-9 Immune System Integration
• Nervous and Endocrine Systems
• Interact with thymic hormones
• Adjust sensitivity of immune response

Figure 22-30 System Integrator: The Lymphatic System
For all body systems, the lymphatic
system provides adaptive (specific)
defenses against infection. The
lymphatic system is an anatomically
distinct system. In comparison, the
immune system is a physiological
system that includes the lymphatic
system, as well as components of the
integumentary, cardiovascular,
respiratory, digestive, and other body
systems. Through immunological
surveillance, pathogens are
continuously eliminated throughout
the body.
The LYMPHATIC System
Distributes WBCs; carries antibodies
that attack pathogens; clotting response
helps restrict spread of pathogens;
granulocytes and lymphocytes
produced in bone marrow
Glucocorticoids have
anti-inflammatory effects; thymosins
stimulate development and
maturation of lymphocytes; many
hormones affect immune function
CardiovascularEndocrineNervousMuscularSkeletal
Microglia present antigens that
stimulate adaptive defenses; glial
cells secrete cytokines; innervation
stimulates antigen-presenting cells
Protects superficial lymph nodes and
the lymphatic vessels in the
abdominopelvic cavity; muscle
contractions help propel lymph along
lymphatic vessels
Lymphocytes and other cells
involved in the immune response are
produced and stored in red bone
marrow
Provides physical barriers to pathogen entry;
macrophages in dermis resist infection and
present antigens to trigger immune response;
mast cells trigger inflammation, mobilize cells
of lymphatic system
Integumentary
Body System Lymphatic System Lymphatic System Body System
S Y S T E M I N T E G R A T O R
Provides IgA antibodies for
secretion onto integumentary
surfaces
Assists in repair of bone after
injuries; osteoclasts differentiate
from monocyte−macrophage cell
line
Assists in repair after injuries
Cytokines affect hypothalamic
production of CRH and TRH
Thymus secretes thymosins;
cytokines affect cells
throughout the body
Fights infections of
cardiovascular organs;
returns tissue fluid to
circulation
Cardiovascular
Page759
Endocrine
Page632
Nervous
Page543
Muscular
Page369
Skeletal
Page275
Integumentary
Page165
Respiratory
Page857Page910Page992
Digestive
Page1072
UrinaryReproductive

169 Ch 22_lecture_presentation

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